It is common for round balers to have a bale forming chamber defined by a pair of opposing side walls associated with an array of side-by-side belts, transverse slats trained on chains, a plurality of rolls or a combination of these various elements, e.g., rolls and belts. During field operation, windrowed crop material such as hay is picked up from the ground and fed into a fixed or variable diameter chamber. The hay is then formed into a cylindrical package, wrapped with twine, net or the like and ejected onto the ground for subsequent handling.
Because it is not uncommon for windrows of crop material to be narrower than the width of the bale forming chamber, it is necessary for the operator to observe the shape of the cylindrical package as it is being formed and to steer the baler along a path that results in uniform transverse distribution of hay to avoid poorly shaped bales. This approach relies on the experience and technique of the operator to determine when to shift the position of the baler relative to the windrow. The lack of exactness, inability to observe the bale shape, reliance on operator skill, and operator fatigue all contribute to the potential for improper feeding resulting in misshaped bales.
During operation of belt type balers, if a substantially uniform diameter is not maintained during feeding, improper tracking occurs which could lead to belt jamming and damage. In addition, unevenly shaped bales cause low density areas on the outer surfaces. This could result in premature deterioration if the bales are exposed to weather extremes, i.e., bales with such low density areas will not shed water as well as those with an evenly shaped and uniformly compacted surface area.
Many present day balers of the various types mentioned above recognize the need for enhancing bale shape. Systems are employed that address the problem of conveniently and consistently forming bales having a substantially uniform diameter throughout their length. This has been accomplished to a certain degree by utilizing monitoring arrangements to ascertain parameters that in turn are used in the control of functions that have a direct bearing on the shape of bales formed. A bale shape control system of this type is disclosed in U.S. Pat. No. 4,748,801, issued Jun. 7, 1988, 1979 in the name of Ronald T. Sheehan, et al. This system includes first and second indicator lights, and bale diameter monitoring apparatus for alternately generating signals in response to predetermined incremental expansion of the bale forming chamber. This enables the operator to position the baler to feed crop to one side of the bale forming chamber when a signal is generated in one indicator and to position the baler to feed crop to the other side of the chamber when a signal is generated in the other indicator.
In U.S. Pat. No. 4,224,867, issued Sep. 30, 1980 in the name of Melvin V. Gaeddert, et al, and U.S. Pat. No. 4,517,795, issued May 21, 1985 in the name of Gerald F. Meiers, similar prior art systems are shown in which a monitor senses tension in belts at both sides of the cylindrical package being formed in the chamber and generates signals directly related to the relative diameters. This enables the operator to steer the baler in a manner that will feed crop material to the area in the chamber that is deficient in an attempt to prevent the bale from becoming improperly shaped.
In another system, disclosed in U.S. Pat. No. 4,686,820, issued Aug. 18, 1987, in the name of Bryan K. Andra, et al, tension on the belts is utilized to generate a signal that is used to control apparatus that varies the path of crop being fed to the bale forming chamber. The baler is driven straight down the windrow, hay is picked up, and as it is being conveyed toward the chamber the stream of hay is selectively deflected into one of three regions of the chamber based on diameter differentials.
In yet another prior art system, disclosed in U.S. Pat. No. 5,131,214, issued Jul. 21, 1992, in the name of Gary J. Vermeer, a crop loading monitor is employed to assist the operator in the formation of round bales. The monitor in this instance comprises an interval timer which signals the operator to direct crop material to alternate sides of the baler at preselected time intervals.
The round baler shape monitoring systems described above either monitor the general baler diameter, various relative diameters or the time interval during which crop is being fed. The present invention is an improvement to a round baler having still another type shape monitoring system, one in which the degree of compaction of crop material in the chamber is monitored. A system of this nature is disclosed in U.S. Pat. No. 5,444,969, issued Aug. 29, 1995 in the name of Robert A. Wagstaff, et al. More particularly, the degree of compaction is sensed by sensors having leaf springs urged against the sides of the cylindrical package of crop material during formation.